The scope of this proposal is to develop a novel and ultra sensitive method for the measurement of DNA adducts quantitatively in humans and to study the degree of benzene and trichloroethylene (TCE) macromolecular adduct formation and repair in adults and children at concentrations equivalent yo human exposure levels. Benzene and TCE are important toxicants in the workplace and are ubiquitous in the environment. Importantly, there may be age- and gender-specific sensitivity to these agents, which requires study to understand the risks posed to children as opposed to adults. Our goal for this project is to develop and validate a method in animals that will have the capacity to quantitatively measure adducts from benzene and TCE exposure in humans and to understand the relationship between age and gender on the dose reaching the target tissues and the resultant levels of macromolecular adducts that are formed at doses equivalent to those encountered around superfund waste sites. Specifically, we will: 1. Develop and validate an accelerator mass spectroscopy-based isotope "post-labeling" assay. This assay will involve chemical acylation of nucleosides or nucleotides, will be quantitative, and will have detection limits in the low attomole range (equivalent to approximately 1 adducts/10/12 nucleotides). This is a continuation of the development of this technology for broad use in toxicology research. 2. Apply this isotope post-labeling-AMS assay in pilot studies using a mouse model to explore age and gender effects on benzene and TCE DNA adduct formation and clearance. 3. Conduct a pilot study with human sperm from benzene exposed workers to assess the mean level and variation in DNA adduct levels. We will correlate DNA adduct levels with exposure dose, subject age, blood protein adducts, and markers of chromosomal damage measured by other projects in this program.